The interplay between active galactic nuclei and star formation activities of type 1 active galactic nuclei probed by polycyclic aromatic hydrocarbon 3.3 μm emission feature with AKARI

Abstract

Abstract We investigate the connection between active galactic nucleus (AGN) and star formation activities of AGN host galaxies by studying the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature of 79 type 1 AGNs using the AKARI space telescope. Utilizing the slitless spectroscopic capability of the AKARI Infrared Camera, we obtained the spectra in the wavelength range of 2–5 μm from extended regions of the sample galaxies in order to measure star formation activity from the entire host galaxies. We detected the 3.3 μm PAH emission feature from 18 sample galaxies and measured the luminosities of the feature (LPAH3.3). We found that LPAH3.3 is significantly correlated with AGN luminosities (LAGN), such as 5100 Å monochromatic luminosity, and X-ray luminosity regardless of host galaxy morphology and radio-loudness. The correlation between LPAH3.3 and LAGN follows $L_{\rm {PAH3.3}} \propto L_{\rm {AGN}}^{0.9}$. Therefore we suggest that host galaxies with stronger AGN activities have stronger star formation activities. We also found that the ratios between LPAH3.3 and the bolometric infrared luminosity (LIR) of our sample galaxies are lower than for non-AGN galaxies due to increased LIR. We suggest that this can be attributed to the contribution of AGN to LIR.